Variable condenser



J y 1929- w. DUBILIER 2 VARIABLE CONDENSER Filed June 10, 1924 ATTORNEY Patented July 30, 1929.

WILLIAM DUBILIER, OF NEW Y 0111:, N. 2:, RADIO eonroaa'rron, or new YORK, .11.

PATENT OFFICE.-

ASSIGNOR TO DUBILIER CONDENSER & Y., A CORPORATION OF DELAWARE.

VARIABLE CONDENSER.

Application filed June 10, 1924. Serial No. 719,115.

This invention relates to improvements in electrical condensers; especiall electrical condensers so designed that t e capacity thereof can be varied as desired, to suit practical conditions.

An object of this invention is to provide a variable electrical condenser which is simplev in structure, which can be conveniently mounted upon a panel or other support, which is easy to operate, and which is so constructed that, upon the parts being adjusted in a pre-determined manner, the condenser will afford, sharpness and accuracy, of capacity required.

Other objects and advantages of this invention will appear from the following description, taken with the drawings, in which the preferred embodiment of my invention is illustrated. But this disclosure is of course explanatory only, and I may make changes in the device actually shown without departing from the scope and spirit of this invention, to the full the precise measure extent indicated by the broad and eneral meanings of the terms in which t pended claims are ex ressed.

On the drawings, igure 1 is a top plan of the exterior of the casing of a variable condenser according to my invention;

Figure. 2 is a longitudinal section on the line 22 of Figure 1;

Figure 3 is a bottom plan of such a condenser;

Fi re 4 is a plan view of a detail, showing t e manner in which the conducting elements of the condenser are disposed in the re uired relation to each other; and

igure 5 is a section taken on the line 5-5 of Figure 4. v

- The same characters on the drawings identifythe same parts throughout.

In the articular-description of the details whic are presented 1n thedrawings, I use the numeral 1 to indicate a casing or e aphousing of suitable form and material, and

within this, casing, I place a pair of sheets or plates of conductive material-2, such as thin metal foil; and associated, with the with the greatest.

accompanying screwed into these .encircle the guide .the nuts 7 and'the surface of the plate 3,

sheets or elements 2 is an operating member in the form of a plate 3 disposed inside the casing 1. This casing is depicted as being closed at the ends and sides, and having a top 4, and enclosing a chamber or space 5 inwhich the movable parts of the condenser are mounted. While the casing 1, the plate 3, and the chamber 5 are shown as being oblong in shape, I may adopt any other form consistent with the purposes which this invention is intended to serve. The plates 2, as indicated in Figures 2, 4 and 5, lie in a single plane and are in longitudinal alinement with each other. They lie between the plate or member 3, and the top 4 and their adjacent ends are separated by a space substantially in the middle of the casing 1; the capacity of the condenser being regulated by bridging this space to a greater or less extent.

The op osite ends of the plate or member 3 are per orated as indicated particularly at the left of this member in Figure 2; and through these perforations are passed guide means or pins 6 which are afiixed to the top 4 of the casing 1. These guide bolts are smooth over substantially their entire length, but are threaded at one end to engage threaded openings in the top 4, and when openings as far as they will go, they engage the casing firmly and become fixed therein. At their opposite ends they may be threaded to receive nuts 7, and encircling each guide pin 6 and situher 3 to push this member towards the top 4.

At each end of the springs 8, washers 9 may pins, thus bearing upon and acting. as seats for the opposite ends of the springs 8. The springs 8, acting\to urge or impel the member. 3 towards the inner surface of the top 4 of the casing, tend to restrict the space between the top 4 and the member 3 within relatively narrow limits.

The elements or sheets of tinfoil 2 are apertures.

placed end toend between two covering sheets of mica or other insulation 10 As stated above, the adjacent ends of the two sheets of foil are separated; while the opposite ends of these two sheets may project beyond the covering sheets of mica andbe bent over upon the outer face of one of'these sheets, as indicated particularly at 11 in Figure 5. The two terminal edges of the'sheets of mica 10 may each be engaged by, a strip of conductive material doubled upon itself along its length, to'provide a clip 12 at each end of the two covering sheets of mica, each clip 12 making electrical connection with the projecting overturned end 11 of the adjacent element 2. At the middle, the two mica sheets are pierced to provide registering apertures 13, and the distance between the adjacent ends of the elements 2 will be slightly greater than the diameter of these The elements 2 with the covering sheets 10, and the clips 12 thus constitute a single structural unit which should be maintained as nearly as possible in a stationary position between the top 4 and member 3'; the. capacity of the condenser being adapted to'be varied by means eo-operating with the elements 2 to bridge the interval between themto the required extent, and also actin to holdithese plates in required relation. uch means have the form of a pair of bent spring plates 14 and 15; the upper plate being of metal of about the same length as the mica covering sheets 11, and of no greater width than this plate, being bent or bowed so that it makes contact with the inside face of the top 4 at its two extremities, but is separated from the top 4 in the middle; while the lower plate 15 is sprung in the reverse direction, that is, it is convex on its upper face, bearing against the lower mica covering sheet 10 in the middle, and against the plate 3 at its opposite ends. The two plates 14 and 15 likewise have apertures in the middle similar to the apertures 13, and in registry with same. Hence, when the plate 3 is forced downward againstthe stress of the springs 8, the plates 14 and 15 act in some degree to become more convex, and their extremities thereby move farther apart from the adjacent faces of the elements 2. On the other hand, when the plate 3-is moved towards the top 4, the springs are more nearly flattened out, and become less convex, and thus their ends are brought into closer proximity to the adjacent faces of the elements 2. Obviously, when the ends of these plates 14 and 15 are permitted to curve away from the elements 2, the capacity of the condenser is decreased; and when the extremities of these springs are moved towards the sheets of foil 2, the capacity of the condenser is enlarged. Owing to the resiliency of the plates 14 and 15, both of which are sprung plates 14 and 15; and while the capacity of the condenser can be varied throughout the entire range of operation, the up-and-down movement of the plates 2, while it may not be entirely eliminated, is restricted and reduced to a minimum. The condenser elements are therefore very effectively mounted, and the wear upon them is practically eliminated. These elements 2 are of course very thin and so areJthe mica covering sheets 10; and on account of their fragile nature, the importance of guarding them against unnecessary stresses and imparting to them no more movement than can be avoided, will be appreciated; for while the elements 2 must be held firmly between the metal parts 14 and 15 and these plates must be allowed to flex in order to vary the capacity of the condenser, the mica sheets 10 must be present to insulate the elements 2, and, to prevent breaks or cracks in the -mica from oc curring, and thus exposing the plates. 2, everything which will stress the mica orbend it, or move it, any more than can be avoided, must be obviated.

The top 4 of the casing has a central protuberance 16, which has a threaded aperture in line with the apertures in the mica, and the plates 14 and 15. This aperture receives the threaded end 17 of a stem 18; the inner extremity of the threaded end 17 passing through the apertures 13 in the mica, and

the. plates 14 and 15; and abutting the center of the member 3 upon its upper surface.

'Hence, by turning the stem 18, the operator.

can force the member 3 downward to compress the s rings 8 and thus diminish the capacity 0 the condenser; while by the turning of the stem 18 in the opposite direction, the threaded end 17 is withdrawn more or less, and the springs 8 are permitted to impel the member 3 towards the top 4 and thus cause the flattening of the springs 14 and 15, to increase the capacity of the condenser. a

The two ends of the casing 1 may be provided with openings to receive insulating bushings 19 at the outer ends of which are insulating washers 20. Inside of the casing 19, against the inner ends of the bushings 19, I may place washers 21 which should be secured, so as to fit along one edge against the top 4, and through these washers, the bushings, 19 and washers 20, are passed sockets ,ed to draw the heads 23 against the washers 21, and force the washers 25 against the washers 20. By means of the binding screws 27, the terminals of an outside circuit can the heads 23 and washers 21 gather, and the washers 21 be joined to the condenser and thus be connected to the elements 2.

The stem 18 may have a pin 28 projecting therefrom, to engage a stop pin 29 .in the top of the protuberance 16, and thus limit the rotation of the stem 18 to one turn. However, I may so construct the condenser that less than one turn, or more than one turn can be allowed according as convenience or circumstances may demand.

At the opposite ends of the condenser, I

may provide projections or lugs 30, with threaded openings 31 therein, to enable the condenser to be secured to a bench, shelf or table, and at the opposite ends of the top, I may provide projections 32, having threaded openings 33, to enable the casing to be secured to a panel. The bottom of the casing is open, and the lower edge thereof has a shoulder 34, extending all around it, to receive a closure plate 35, to be held in place by any suitable means.

If desired, the condenser may be provided on the interior at the opposite sides thereof with vertical ribs 36, to enable the plate 3 to fit the chamber 5 more closely. I also prefer to make the heads 23 of the sockets 22 square, and to provide the washers 21 with projections 37 from their faces, to engage one side of the heads 23. Then, when the outer ends of the sockets are expanded,

are forced toare held tightly against the inner faces of the ends of the casing, so that when the binding screws 27 are tightened, the sockets will not turnor twist in the ends of the casing.

From the foregoing, it will be seen that the construction of the condenser is comparatively simple, while the adjustment afforded is very accurate. The principal parts of the condenser are well protected in. the casing 1, while connection to the outside .can conveniently be made. Through 14 and 15, the capacity can be varied with certainty, and the device is not likely to get out of order; but on the contrary, the movement of the stem 18 and the member 3 to any the plates 14 and 15.

condenser which is intermediate the means provided in the form of the plates 1 particular position will always give the same result; that is to say, the turning of the stem 18 through any given arc will always cause the same amount of capacity to be given by the plates 2, in combination with In this class of condensers, the operation of the device"must be attended with the greatest certainty and therefore the parts must be proportioned and assembled so that they will always operate in the same way, iving a pre-determined amount of capacity $01 every separate position which they may occupy; for if certainty of operation were not secured, the condenser would give one capacity with the parts in a particular position at one time, and adifferent capacity with the same parts in the same position at another time, as is well understood by those skilled in this art. All of'the advantages referred to are obtained in the practice of my invention, with a construction such as is above described.

In Figure 2, the plates 14 and 15 and the sheets of tin-foil 2 and sheets of mica 10 and 11, together with the parts 12 are shown in side or edge view, and not in'section, for the sake of, convenience and clearness. It is to be understood of course, that the plates 10, 11, 14 and 15 are. substantially the same 1shape and same width as the operating mem- Having described my invention what I believe to be new and desire to secure and rotect by Letters Patent of the United tates is l. A condenser comprising electrically conductive elements having adjacent ends, an electrically conductive part insulated from said elements and movable into close proximity to a larger or smaller portion of said elements to vary the capacity of the and an operating member adapted to exert pressure directly upon the ex-( tremities of saidpart and control the position of the same.

2. A condenser comprising electrically conductive elements having adjacent ends and an electrically conductive part, the middle of which is situated intermediate of said ends and an operating member adapted to cause pressure to be exerted directly upon the extremities of said part to cause the part to be,moved into close proximity to a middle of said face intermediate said eleto a larger or smaller portion of said elements beginning at said ends, to vary the capacity ,of the condenser.

4. A condenser comprising electrically conductive elements having adjacent ends, an electrically conductive plate presenting a convex face towards said elements with the ments and an operating member to engage the extremities ofl-fs'aid plate to force said extremities towards said elements and thus vary the capacity of the condenser.

5. A condenser comprising electrically conductive elements having adjacent ends, a

plate of electrically conductive material presenting a convex surface toward one face of each of said elements, a similar plate presenting a convex surface towards the opposite faces of each of said elements, the middle portions of said plates being intermediate the adjacent ends of said elements, and an operating member to cause pressure to be exerted upon the extremities of the plates and move the extremities of said plates towards said elements to vary the capacity .of the condenser, said elements being displaceably held between said plates.

6. A condenser comprising electrically conductive elements in a single plane with their adjacent ends spaced apart, a spring plate presenting a convex surface to one face of each of said elements and having its middle portion in proximity to said adjacent ends, a spring plate presenting a convex surface to opposite faces of said elements, having its middle portion in proximity to said adjacent ends, the elements being di splaceably held between said plates, a cas-' ing in which said elements and said plates are disposed, an operating member in the casing adapted to cause pressure to be exerted upon the extremities of the plates to lessen the convexity of the same and cause them to be moved into proximity to a larger portion of said elements to vary the capac- 'itj'bf said condenser, and guiding means for said member.

. located between said member and the top of the casing, a spring plate of conductive material between said member and said elements and presenting a convex surface to said elements; the middle of said plate being in proximit to said adjacent ends, an-

. other spring p ate of conductive material between said elements and the top of the casing and presenting a convex surface to said elements, the middle of last-named plate being in proximity to said adjacent ends, the extremities of the first plate resting upon the operating member and the extremities of the second plate resting against the'top, whereby pressure on said member acting towards the plates causes force to be exerted upon said plates to lessen the curvature thereof, and a shaft to engage the operating member to move it away from socket and insulating sleeve" surrounding said socket, washers at the outer ends of said sleeve, the sockets'each being hollow and being expanded at the outer ends to hold the washers adjacent said outer ends against said sleeve; a head at'the inner end of each socket and a washer between said head and the inner end of each sleeve in the casing to engage the inside of the casing and be so engaged by said head as to prevent rotation of the washer.

9. A condenser comprising electrically conductive elements having adjacent ends and a curved spring plate, the middle of which is intermediate said ends, said plate having a curved face which is presented to said elements, so that when pressure is exerted directly on said plate to move it toward said elements, said plate will be brought into closeproximity to .a larger or smaller portion of said elements to vary the capacity of the condenser.

10. A condenser comprising electrically conductive elements having adjacent ends, an electrically conductive plate presenting a curved face towards said elements with the middle of said face intermediate said ele-- ments, and an operating member adapted directly to engage said plate to force said plate towards saidelements and thus vary the capacity of the condenser.

11. A condenser comprising electricallyv conductive elements having adjacent ends, a plate of electrically conductive material presenting a curved surface toward one face of each of said elements, a similar plate presenting a curved surface towards each of the opposite faces of said elements, the middle portions of said plates being intermediate the adjacent ends of said elements, and an operating member adapted to cause pressure to be exerted upon the plates and move the plates towards said eleinents to vary the capacity' of the condenser.

12. A condenser comprising electrically conductive elements in a single plane with their adjacent ends spaced apart, a'spring plate presenting a curved surface to the faces of said elements and having its middle portion. in proximity to said ends, a

spring plate presenting a curved surface to opposite faces of said elements, having its middle portion in proximity to said adjacent ends, a casing in which said elements and said plates are disposed, and an operating member in the casing adapted to cause pressure to be exerted upon the plates to lessen WILLIAM DUBILIER. 

